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From Sudhakar Thota <sth...@maprtech.com>
Subject Re: more on parsing timestamps
Date Thu, 02 Apr 2015 20:27:19 GMT
Vince/Andries,

Perhaps this could be a bug. I get the same results. 

But the plan is very different, the UnionExchange is set up immediately after the scan operation
in successful case( Case -1 ), where as UnionExchange is happening after scan->project
(Case -2).

Case -1.Successful case.

0: jdbc:drill:> explain plan for select to_timestamp(t.t, 'YYYY-MM-dd''T''HH:mm:ss.SSS''Z''')
FROM (select * from dfs.sthota_prq.`/tstamp_test/*.parquet` limit 13015351) t;
+------------+------------+
|    text    |    json    |
+------------+------------+
| 00-00    Screen
00-01      Project(EXPR$0=[TO_TIMESTAMP(ITEM($0, 't'), 'YYYY-MM-dd''T''HH:mm:ss.SSS''Z''')])
00-02        SelectionVectorRemover
00-03          Limit(fetch=[13015351])
00-04            UnionExchange
01-01              Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath [path=maprfs:/mapr/demo.mapr.com/user/sthota/parquet/tstamp_test/1_2_0.parquet],
ReadEntryWithPath [path=maprfs:/mapr/demo.mapr.com/user/sthota/parquet/tstamp_test/1_1_0.parquet],
ReadEntryWithPath [path=maprfs:/mapr/demo.mapr.com/user/sthota/parquet/tstamp_test/1_0_0.parquet]],
selectionRoot=/mapr/demo.mapr.com/user/sthota/parquet/tstamp_test, numFiles=3, columns=[`*`]]])
 | {
  "head" : {
    "version" : 1,
    "generator" : {
      "type" : "ExplainHandler",
      "info" : ""
    },
    "type" : "APACHE_DRILL_PHYSICAL",
    "options" : [ ],
    "queue" : 0,
    "resultMode" : "EXEC"
  },

Case -2. Unsuccessful case:
  
0: jdbc:drill:> explain plan for select to_timestamp(t.t, 'YYYY-MM-dd''T''HH:mm:ss.SSS''Z''')
FROM (select * from dfs.sthota_prq.`/tstamp_test/*.parquet` ) t;
+------------+------------+
|    text    |    json    |
+------------+------------+
| 00-00    Screen
00-01      UnionExchange
01-01        Project(EXPR$0=[TO_TIMESTAMP(ITEM($0, 't'), 'YYYY-MM-dd''T''HH:mm:ss.SSS''Z''')])
01-02          Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath [path=maprfs:/mapr/demo.mapr.com/user/sthota/parquet/tstamp_test/1_2_0.parquet],
ReadEntryWithPath [path=maprfs:/mapr/demo.mapr.com/user/sthota/parquet/tstamp_test/1_1_0.parquet],
ReadEntryWithPath [path=maprfs:/mapr/demo.mapr.com/user/sthota/parquet/tstamp_test/1_0_0.parquet]],
selectionRoot=/mapr/demo.mapr.com/user/sthota/parquet/tstamp_test, numFiles=3, columns=[`*`]]])
 | {
  "head" : {
    "version" : 1,
    "generator" : {
      "type" : "ExplainHandler",
      "info" : ""
    },
    "type" : "APACHE_DRILL_PHYSICAL",
    "options" : [ ],
    "queue" : 0,
    "resultMode" : "EXEC"
  },
  
Thanks
Sudhakar Thota


On Apr 2, 2015, at 12:01 PM, Vince Gonzalez <vince.gonzalez@gmail.com> wrote:

> Ok, will do. Thanks.
> 
> On Thu, Apr 2, 2015 at 2:49 PM, Andries Engelbrecht <
> aengelbrecht@maprtech.com> wrote:
> 
>> Compare the query plans and you probably want to look at the log file to
>> see what fails and post here.
>> 
>> 
>> 
>> —Andries
>> 
>> 
>> On Apr 1, 2015, at 12:54 PM, Vince Gonzalez <vince.gonzalez@gmail.com>
>> wrote:
>> 
>>> Is this a bug?
>>> 
>>> Created a parquet table (using CTAS) with one column containing text
>>> timestamps.
>>> 
>>> 0: jdbc:drill:zk=localhost:2181> select * from tstamp_test limit 1;
>>> +------------+
>>> |     t      |
>>> +------------+
>>> | 2015-01-27T13:43:53.000Z |
>>> +------------+
>>> 1 row selected (0.119 seconds)
>>> 
>>> The below queries, identical apart from the limit clause, behave
>>> differently. The one with the limit clause works, the one without
>> doesn't.
>>> The limit is larger than the total number of rows, so in both cases we
>>> should be processing all rows.
>>> 
>>> No limit clause. It fails:
>>> 
>>> ```
>>> 0: jdbc:drill:zk=localhost:2181> select to_timestamp(t.t,
>>> 'YYYY-MM-dd''T''HH:mm:ss.SSS''Z''') FROM (select t from tstamp_test) as
>> t;
>>> Query failed: RemoteRpcException: Failure while trying to start remote
>>> fragment, Expression has syntax error! line 1:30:mismatched input 'T'
>>> expecting CParen [ 7d30d753-0822-4820-afd0-b7e7fe5e639c on
>>> 192.168.99.1:31010 ]
>>> ```
>>> 
>>> Limit clause in the subselect (larger than the number of rows in the
>> table)
>>> succeeds.
>>> 
>>> ```
>>> 0: jdbc:drill:zk=localhost:2181> select to_timestamp(t.t,
>>> 'YYYY-MM-dd''T''HH:mm:ss.SSS''Z''') FROM (select t from tstamp_test limit
>>> 100000000) as t;
>>> ...
>>> | 2015-02-17 07:18:00.0 |
>>> +------------+
>>> 13,015,350 rows selected (105.257 seconds)
>>> ```
>>> 
>>> Data can be downloaded here:
>>> 
>>> https://s3.amazonaws.com/vgonzalez/data/tstamp_test.tar.gz
>> 
>> 


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